1. Field of the Invention
The field of the invention is a system for and method of converting imaging or scanned data from a medical imaging device, and more particularly, is a system for and method of converting imaging or scanned data from a medical imaging device from a polar format to a Cartesian format.
2. Background
In diagnosing and treating patients, physicians and surgeons are often limited by what they can actually see in the patient. Medical imaging instruments have provided doctors with visualization of a patient's internal structures without the need for major invasive surgery to gain access to those internal structures. Such medical imaging instruments, for example, may be inserted into a patient's body through a natural orifice or a small laparoscopic incision. These medical imaging instruments typically use rotating imager or circular array of imagers in order to provide a three-dimensional view. The medical imaging instrument can use any form of energy to image the area including, for example, acoustic, light, magnetic, thermal, and x-ray energy.
An example of an acoustic medical imaging instrument is a catheter with an ultrasound transducer, is well known in the art; see, e.g., U.S. Pat. No. 5,400,785, entitled “Acoustic Window and Septum for Imaging Catheters”, which is assigned to Boston Scientific Corporation, the entirety of which patent is incorporated herein by reference for all purposes.
An example of a light energy based medical imaging instrument is one using optical coherence tomography (OCT), which is well known in the art; see, e.g., U.S. Pat. No. 5,459,570, entitled “Method and Apparatus for Performing Optical Measurements,” assigned to Massachusetts Institute of Technology; U.S. Pat. No. 5,321,501, entitled “Method and Apparatus for Optical Imaging with Means for Controlling the Longitudinal Range of the Sample,” assigned to Massachusetts Institute of Technology; U.S. Pat. No. 6,384,915, entitled “Catheter Guided by Optical Coherence Domain Reflectometry”, and assigned to the Regents of the University of California, the entirety of each of which are incorporated herein by reference for all purposes. OCT is an optical imaging technique, which achieves non-invasive, cross-sectional imaging of a patient's body. OCT is analogous to ultrasound imaging, but measures the intensity of back-scattered infrared light rather than acoustic waves. To image the blood vessel of a patient using OCT, an optical catheter is inserted into the blood vessel. An optical signal is transmitted through an optical fiber in the optical catheter and emitted at the distal end of the catheter into the blood vessel. The optical signal is typically produced by a laser, e.g., laser diode. The optical signal reflected back to the catheter from the blood vessel and surrounding tissue is transmitted through the optical fiber to an interferometer, which optically processes the reflected optical signal to obtain a depth image of the blood vessel. The optical signals produced by the light source, e.g., a laser, into the catheter optical fiber to be emitted inside the body. The OCT connection system then couples the reflected optical signal out of the catheter optical fiber to an interferometer to obtain a image of the inside of the body. In addition, the OCT connection system may include a motor unit for providing drive torque to the catheter optical fiber to rotate the catheter optical fiber during imaging. This enables a radial cross-sectional image of the inside of the body to be obtained. See also, Tearney, G. J., et. al, “Scanning Single-Mode Fiber Optic Catheter-Endoscope for Optical Coherence Tomograph,” Optics Letters 21 (7): 543-545 (1996), the entirety of which is incorporated herein by reference for all purposes.
Optical coherence domain reflectometry (OCDR) has also been used for medical imaging. Likewise, other optical imaging approaches include optical time domain reflectometry (OCTR), scanning laser microscopes, scanning confocal microscopes, scanning laser ophthalmoscopes and optical triangulation. See, e.g., Youngquist R. C., et al. in “Optical Coherence-Domain Reflectometry: A New Optical Evaluation Technique,” Optic Letters 12(3):158-160 (1987); Danielson, B. L., et. al, “Guided-Wave Reflectometry with Micrometer Resolution”, Applied Physics 26(14): 2836-2842 (1987). The entirety of each of these references are incorporated herein by reference for all purposes.
An example of a magnetic medical imaging instrument is a magnetic resonance imaging device (MRI), which is well known in the art; see, e.g., U.S. Pat. No. 5,928,145, entitled “Method of Magnetic Resonance Imaging and Spectroscopic Analysis and Associated Apparatus Employing a Loopless Antenna”, assigned to the Johns Hopkins University. X-ray medical imaging instruments are well known in the art. The entirety of each of these patents are incorporated herein by reference for all purposes.
The rotating imager takes snapshots of the patient's internal structures, which snapshots are often in a polar format. In other words, the rotating imager takes a series of images at different radii, rotates to a new position and takes another series of images at various radii, and repeats the process. Thus, in a polar format, the axes of the image are the angle theta θ at which the rotating imager has rotated from the initial starting position and the radius along that angle. The human brain has difficulty viewing, recognizing and comprehending polar images because humans are used to Cartesian formats, that is, where the axes are spatially oriented in two or three dimensions. As a result, polar images must be converted to Cartesian format so that doctors and health care professionals can understand the images for diagnostic purposes. However, the prior art systems and methods for converting polar images have been very complex and expensive, as well as requiring significant custom hardware. An example of a prior art medical image processing system 2 is shown in FIG. 1, having a monitor 3, keyboard 4 and body 5. The size of the body 5 of the system in FIG. 1 indicates the amount of hardware needed to process and convert the images.
Therefore, there is a need for a simpler, cheaper system and method for converting polar imaging data from a medical imaging device to a Cartesian format.